STCE Newsletter

1. Solar hemispheric asymmetry
2. Review of solar and geomagnetic activity
3. International Sunspot Number by SILSO
4. PROBA2 Observations
5. Noticeable Solar Events
6. Geomagnetic Observations in Belgium
7. Review of Ionospheric Activity
8. The SIDC Space Weather Briefing
9. Upcoming Activities

Solar hemispheric asymmetry

SILSO, the World Data Center for the production, preservation and dissemination of the international sunspot number (https://www.sidc.be/SILSO/home ), has issued its monthly report for July 2024. The provisional sunspot number for last month is 196.5, which is the highest monthly value since December 2001, i.e. near the maximum of solar cycle 23 (SC23 - SILSO table at https://www.sidc.be/SILSO/cyclesminmax ). The highest daily value was recorded on 18 July (290), a value not seen since 27-29 July 2002 when the daily sunspot numbers varied between 290 and 310. The SILSO graph underneath shows the daily, monthly, and smoothed monthly sunspot numbers since mid-2011. The forecasts (dashed lines) now give a smoothed maximum for SC25 of 137-144 during the May-September 2024 timeframe. With the number of sunspots already observed so far in August, this maximum may turn out to be even higher.

The observed sunspot activity has been driven by a plethora of active regions in the southern hemisphere. This domination over the northern hemisphere only started a few months ago, and continued into August. The comparison underneath (SDO/HMI - http://sdo.gsfc.nasa.gov/data/aiahmi/ ) shows the Sun's appearance in white light a year ago (20 July 2023 - left) and currently (6 August 2024 - right). This domination (aka hemispheric asymmetry) can last for years as shown in these plots at SILSO (https://www.sidc.be/SILSO/monthlyhemisphericplot ) and the STCE's SC25 tracking page (https://www.stce.be/content/sc25-tracking#hemi ).

The domination of the southern solar hemisphere is also visible in other parameters, such as the number of solar flares (M- and X-class). The graph underneath clearly shows how -in 2023- most of the flares were produced in the northern solar hemisphere, whereas from early 2024 onwards the southern hemisphere has taken over with the largest monthly number of flares so far this solar cycle. In May, no less than 143 M- and X-class flares have been recorded, 99 of which in the southern solar hemisphere and -mostly- courtesy of the super group NOAA 3664 (https://www.stce.be/news/704/welcome.html ). Interestingly, the last data point is only for the first 4 days of August and far from complete. Yet, the flare numbers are already close to some of the monthly flare numbers in the northern hemisphere for an entire month!... Impressive.

Review of solar and geomagnetic activity

WEEK 1231 from 2024 Jul 29

Solar Active Regions (ARs) and flares

Solar flaring activity has been at high levels throughout the week, with one X-class flare and 48 M-class flares recorded. The strongest flare was an an X1.5 flare peaking at 02:37 UTC on July 29, most likely associated either with NOAA AR 3764 (beta) or 3766 (beta). There was a total of 18 numbered active regions on the visible disk, many of them developing to a complex magnetic type beta-gamma-delta (NOAA ARs 3762, 3765, 3766, 3767, 3768, 3772, 3774) during the week. Of particular interest was a cluster of complex active regions (NOAA ARs 3763 to 3767), which rotated behind the west limb towards the end of the week.

Coronal Mass Ejections

Multiple Coronal Mass Ejections (CMEs), filament and prominence eruptions were recorded during the last week. Selected events are listed below.
A halo CME was observed in LASCO/C2 coronagraph imagery around 15:10 UTC on July 28. Another faint partial halo CME was first observed in LASCO/C2 coronagraph imagery around 02:40 UTC on July 29. A related type II Radio emission was reported, starting at 02:36 UTC, with an estimated velocity of 535 km/s. A CME was observed in LASCO/C2 coronagraph imagery around 13:36 UTC on July 29, probably associated with an M8.7 flare from NOAA AR 3762. A CME was observed in LASCO/C2 coronagraph imagery around 15:33 UTC on July 29, associated with a filament eruption in the southwest quadrant, south of NOAA AR 3768. A wide CME was observed in LASCO/C2 coronagraph imagery around 07:15 UTC on July 31, lifting off the southeast limb. It was probably associated with the M7.7 flare which peaked at 06:46 UTC on July 31, from NOAA AR 3768. A partial halo CME was observed in LASCO/C2 coronagraph imagery around 18:48 UTC on July 31, lifting off the west limb. It was likely associated with an M5.3 flare peaking at 18:37, from NOAA AR 3768. A related type II radio emission was observed, starting at 18:20 UTC on July 31 with an estimated velocity of 326 km/s. An associated type IV radio emission was observed, starting at 18:31 UTC on July 31. A partial halo CME was observed in LASCO/C2 coronagraph imagery around 06:40 UTC on August 01, lifting off the west limb. It was most likely associated with an M8.2 flare from NOAA AR3768, starting at 06:20 UTC and peaking at 07:09 UTC on August 01. An associated type II radio emission was observed, starting at 07:12 UTC on August 01 with an estimated velocity of 739 km/s. A related type IV radio emission was observed, starting at 07:08 UTC on August 01. A wide CME was observed in LASCO/C2 and LASCO/C3 coronagraph imagery starting from 21:42 UTC on August 01, lifting off the northeast quadrant. It was possibly associated with a filament eruption near NOAA AR 3775. A partial halo CME was observed in LASCO/C2 and LASCO/C3 coronagraph imagery starting from 04:17 UTC on August 02. It was likely associated with flaring activity near the west limb from NOAA ARs 3768 or 3773. A related type II radio emission was observed, starting at 04:49 UTC on August 01, with an estimated velocity of 438 km/s. A related type IV radio emission was observed, starting at 04:57 UTC on August 01.
A large filament eruption was observed around 18:40 UTC on August 02 in AIA 304 data, in the southwest quadrant. A prominence eruption was observed around 23:55 UTC on August 02 in AIA 304 data, in the east limb, near the equator. A second filament eruption was observed around 01:45 UTC on August 03 in AIA 304 data, in the northwest quadrant near NOAA AR 3770. No associated coronal mass ejections (CMEs) were observed in the available coronagraph imagery for these events. Three filament eruptions were observed in AIA data on August 03 and August 04. The first was a filament eruption around 12:15 UTC on August 03 in the south hemisphere, near the central meridian. The second filament eruption was recorded around 13:49 UTC on August 03 near NOAA AR 3777. The third filament eruption was observed around 00:20 UTC on August 04, near NOAA AR 3775. Last, a large prominence eruption was recorded around 04:42 UTC on August 04, in the southwest limb.

Coronal Holes

Two coronal holes have appeared on the visible disk during the week. The first was a high-latitude, negative polarity coronal hole which fully crossed the central meridian on August 01. The second was an equatorial, negative polarity coronal hole which started to cross the central meridian late on August 04.

Proton flux levels

The greater than 10 MeV GOES proton flux was below the 10 pfu threshold throughout the week, with small enhancements between 05:30-16:00 UTC on August 01 and between 01:00-15:30 UTC on August 02. It remained at background levels until the end of the week.

Electron fluxes at GEO

The greater than 2 MeV electron flux seen by GOES-18 was over the threshold between 16:45 UTC on July 29 and 02:00 UTC on July 30. The greater than 2 MeV electron flux seen by GOES-16 at the same time was close to the threshold level but remained below it. For the rest of the week, the greater than 2 MeV electron flux remained below the 1000 pfu threshold as measured by GOES 16 and GOES 18. The 24-hour electron fluence was at nominal levels throughout the week.

Solar wind

A shock was detected in the solar wind data (DSCOVR and ACE) around 23:20 UTC on July 29. The interplanetary magnetic field jumped from 4 nT to 14 nT, with the Bz component changing from -3 nT to 11 nT and then decreasing up to -12 nT. The solar wind speed jumped from 350 km/s to 440 km/s and increased up to 500 km/s. The solar wind density at the shock jumped from 1.84 ppcc to 7.25 ppcc and increased up to around 15 ppcc. The shock was probably related to an interplanetary coronal mass ejection (ICME) arrival, associated with one of the CMEs detected between July 27-28.
The solar wind conditions were enhanced again starting early on August 04, probably due to a glancing blow arrival from a coronal mass ejection that lifted off the Sun on July 31. Speed values reached a maximum of around 480 km/s and the interplanetary magnetic field a maximum of 15 nT. The Bz component reached -15 nT.

Geomagnetism

Geomagnetic conditions globally reached minor storm levels (NOAA Kp 5) between 03:00-06:00 UTC on July 30 and at 18:00 UTC on July 31 until 06:00 on August 01, in response to interplanetary coronal mass ejection (ICME) arrivals. At the same intervals, geomagnetic conditions locally reached active levels (K Bel 4).
Geomagnetic conditions globally reached major storm levels (NOAA Kp 7-) between 12:00-15:00 UTC on August 04, in response to a glancing blow arrival from the CME that lifted off the Sun on July 31. At the same time, geomagnetic conditions locally reached minor storm levels (K Bel 5).

International Sunspot Number by SILSO

The daily Estimated International Sunspot Number (EISN, red curve with shaded error) derived by a simplified method from real-time data from the worldwide SILSO network. It extends the official Sunspot Number from the full processing of the preceding month (green line), a few days more than one solar rotation. The horizontal blue line shows the current monthly average. The yellow dots give the number of stations that provided valid data. Valid data are used to calculate the EISN. The triangle gives the number of stations providing data. When a triangle and a yellow dot coincide, it means that all the data is used to calculate the EISN of that day.

PROBA2 Observations

Solar Activity

Solar flare activity ranged from moderate to high throughout the week. An unusually high number of active regions were observed on the solar disk, with several producing M-class flares. On several occasions, flares occurred in different regions in close succession, suggesting the possibility of sympathetic events.

In order to view the activity of this week in more detail, we suggest to go to the following website from which all the daily (normal and difference) movies can be accessed: https://proba2.oma.be/ssa
This page also lists the recorded flaring events.

A weekly overview movie can be found here (SWAP week 749). https://proba2.sidc.be/swap/data/mpg/movies/weekly_movies/weekly_movie_2024_07_29.mp4

Details about some of this week's events can be found further below.
If any of the linked movies are unavailable they can be found in the P2SC movie repository here: https://proba2.sidc.be/swap/data/mpg/movies/

Monday Jul 29

The biggest flare of the week, a X1.5, occurred around 2:37UT. It was produced by the NOAA active region 3766 located at S05W04. The LYRA time series and the SWAP image show the large event. Find a SWAP movie of the event here: https://proba2.sidc.be/swap/movies/20240729_swap_movie.mp4

Wednesday Jul 31

A filament eruption occurred in the South-West part of the solar disk around 00:20 UT, immediately followed by a prominence eruption on the S-W limb. Find a SWAP movie of the event here: https://proba2.sidc.be/swap/movies/20240731_swap_movie.mp4

Saturday Aug 3

A M7.3 solar flare was observed in NOAA active region 3775 around 18:39 UT in the North East part of the solar disk. Another event, a M5.4 flare, happened shortly after at the East limb. Find a SWAP movie of the event here: https://proba2.sidc.be/swap/movies/2024070803_swap_movie.mp4

Sunday Aug 4

Plasma flows were observed in a giant prominence on the south west limb around 04:24 UT, highlighting the complex configuration and the magnetic connection of the structure with the whole region. This event did not result in an eruption, though. Find a SWAP movie of the event here: https://proba2.sidc.be/swap/movies/20240804_swap_movie.mp4

Noticeable Solar Events

DAY	BEGIN	MAX	END	LOC	XRAY	OP	10CM	TYPE	Cat	NOAA
29	0233	0237	0243	S5W4	X1.5	2B		II/2	32	3766
29	0510	0520	0528	S14W36	M1.0	SF		III/2	37	3768
29	1216	1222	1229	S11W56	M1.6	SF			26	3762
29	1247	1255	1304		M8.7			III/3II/1IV/1	26	3762
29	1404	1446	1509	S12W4	M4.2	1N		IV/2		3772
29	1940	1957	2010		M6.4					3772
29	2055	2100	2106	S14W48	M1.1	SF			37	3768
30	0052	0103	0120		M1.7			VI/2	26	3762
30	0130	0132	0136		M1.3				26	3762
30	0616	0629	0646	S7W13	M1.5	SF		VI/1	32	3766
30	0120	0125	0130		M1.2				26	3762
30	0135	0140	0144		M1.4			VI/2	32	3766
30	1612	1628	1642	S8W27	M1.5	1F			32	3766
30	1910	1920	1925	S4W29	M1.9	SN		V/3	30	3764
30	1925	1938	2004	S24E64	M9.4	2N		V/3		3772
31	0143	0150	0154		M1.9					3773
31	0507	0523	0538	S4E83	M4.7	SF		VI/2		3774
31	0628	0646	0658		M7.7			V/3III/3CTM/2	37	3768
31	1245	1305	1326	S22E55	M6.0	1N		III/2		3772
31	1326	1332	1337	S22E55	M4.4	1N				3774
31	1610	1631	1641	S15W68	M1.4	SF				3774
31	1805	1837	1858	S15W71	M5.3	SF		II/2III/2IV/2	37	3768
31	2136	2155	2210	S15W71	M1.2	SF		III/2	35	3767
31	2242	2250	2259		M1.0					3774
01	0050	0058	0103		M1.2			III/1		3770
01	0147	0150	0154		M6.3			V/3		3773
01	0258	0306	0314		M1.2					3774
01	0359	0409	0423		M1.9					3774
01	0435	0441	0445		M4.0			III/2	35	3765
01	0552	0556	0600	S12W35	M1.5	SF		III/2	37	3768
01	0623	0709	0739	S16W74	M8.2	1N		III/2IV/2II/2	37	3768
31	1807	1837	1857	S15W71	M5.4	SF		II/2III/2IV/2	37	3768
01	1109	1137	1141	S16W80	M4.1	SF			37	3768
01	1141	1147	1151	S16W80	M4.1	SF				3772
01	1604	1615	1619	S5W53	M1.0	SF			30	3764
01	1633	1637	1644	S8W41	M1.3	SF			35	3765
01	1722	1729	1734	S3E63	M1.3	SF				3774
01	2012	2022	2032	S13E63	M1.2	SF				3774
01	2300	2308	2317	S21E37	M1.4	SF				3772
02	0154	0201	0208		M1.0				35	3765
02	0317	0325	0331		M1.1					3772
02	0353	0358	0403		M1.1			III/1	37	3768
02	0423	0455	0535	S23E32	M7.3	SF		IV/1	37	3768
02	0751	0759	0803	S8W48	M2.1	SF		III/1	35	3765
02	0908	0916	0928	S26E32	M1.2	SF				3772
02	0945	0951	0955	S6W57	M1.6	SN			32	3766
02	1228	1233	1238	S8W79	M1.2	SF				3773
02	1344	1350	1400	N19E43	M1.1	SN		VI/1		3775
02	1521	1530	1535	S6W60	M1.5	SN		VI/1	32	3766
03	0022	0027	0032	S10E64	M1.0	SF				3777
02	2341	2358	0022		M1.3
03	0445	0459	0505	N9W59	M1.5	SF				3770
03	0652	0705	0711		M1.5					3770
03	0711	0730	0734		M1.9					3770
03	1326	1343	1355	S9E44	M1.8	2N				3774
03	1649	1654	1658		M2.8			VI/2		3770
03	1713	1726	1734		M1.9				32	3766
03	1829	1839	1844		M7.3			III/1		3775
03	1917	1930	1943		M5.4			VI/1
04	0145	0159	0217		M1.4					3781
04	0935	0944	0948		M1.2					3765
04	0948	1001	1003		M1.1					3766
04	1003	1008	1012		M1.4			III/1		3766
04	1027	1050	1124	S18W71	M1.9	SF		VI/2		3781
04	1511	1515	1519	S9E69	M2.2	SN		V/3III/3		3780
04	2204	2211	2215	S9E66	M1.0	SN		V/2II/3III/3		3780

LOC: approximate heliographic location	TYPE: radio burst type
XRAY: X-ray flare class	Cat: Catania sunspot group number
OP: optical flare class	NOAA: NOAA active region number
10CM: peak 10 cm radio flux

Geomagnetic Observations in Belgium

Local K-type magnetic activity index for Belgium based on data from Dourbes (DOU) and Manhay (MAB). Comparing the data from both measurement stations allows to reliably remove outliers from the magnetic data. At the same time the operational service availability is improved: whenever data from one observatory is not available, the single-station index obtained from the other can be used as a fallback system.
Both the two-station index and the single station indices are available here: http://ionosphere.meteo.be/geomagnetism/K_BEL/

Review of Ionospheric Activity

VTEC time series at 3 locations in Europe from 29 Jul 2024 till 4 Aug 2024

The top figure shows the time evolution of the Vertical Total Electron Content (VTEC) (in red) during the last week at three locations:
a) in the northern part of Europe(N 61deg E 5deg)
b) above Brussels(N 50.5deg, E 4.5 deg)
c) in the southern part of Europe(N 36 deg, E 5deg)
This top figure also shows (in grey) the normal ionospheric behaviour expected based on the median VTEC from the 15 previous days.

The time series below shows the VTEC difference (in green) and relative difference (in blue) with respect to the median of the last 15 days in the North, Mid (above Brussels) and South of Europe. It thus illustrates the VTEC deviation from normal quiet behaviour.

The VTEC is expressed in TECu (with TECu=10^16 electrons per square meter) and is directly related to the signal propagation delay due to the ionosphere (in figure: delay on GPS L1 frequency).
The Sun's radiation ionizes the Earth's upper atmosphere, the ionosphere, located from about 60km to 1000km above the Earth's surface.The ionization process in the ionosphere produces ions and free electrons. These electrons perturb the propagation of the GNSS (Global Navigation Satellite System) signals by inducing a so-called ionospheric delay.

See http://stce.be/newsletter/GNSS_final.pdf for some more explanations; for more information, see https://gnss.be/SpaceWeather

The SIDC Space Weather Briefing

The forecaster on duty presented the SIDC briefing that gives an overview of space weather from July 28 to August 4.

The pdf of the presentation can be found here: https://www.stce.be/briefings/20240805_SWbriefing.pdf

Upcoming Activities

Courses and presentations with the Sun-Space-Earth system and Space Weather as the main theme. We provide occasions to get submerged in our world through educational, informative and instructive activities.

* Sep 27, STCE at the Wisenight Science festival in the Planetarium, Brussel, https://wisenight.eu/
* Sep 30 - Oct 3, STCE Space Weather Introductory Course, Brussels, Belgium - Registrations are open https://events.spacepole.be/event/204/
* Nov 25 - 27, STCE course: Space Weather impacts on ionospheric wave propagation, focus on GNSS and HF, Brussels, Belgium - Registrations are open, https://events.spacepole.be/event/206/
* Dec 5-6, STCE Course Space Weather impacts on aviation, Brussels, Belgium - Registrations are open, https://events.spacepole.be/event/205/

To register for a course or lecture, check the page of the STCE Space Weather Education Center: https://www.stce.be/SWEC

If you want your event in the STCE newsletter, contact us: stce_coordination at stce.be